The present technology relates to imaging systems and methods for decoding symbols, and more specifically, to imaging systems and methods for reading two-dimensional matrix symbols with incomplete or absent fixed patterns.
Imaging systems use image acquisition devices that include image sensors to deliver information on a viewed subject. The system then interprets this information according to a variety of algorithms to perform a programmed decision-making and/or identification function. For an image to be most-effectively acquired by a sensor in the visible, and near-visible light range, the subject is typically illuminated.
Symbology reading (also commonly termed “barcode” scanning) using an image sensor, entails the aiming of an image acquisition system including optics (lenses) and a sensor (CMOS camera, CCD, etc.) at a location on an object that contains a symbol (a “barcode” for example), and acquiring an image of that symbol. The symbol contains a set of predetermined patterns that represent an ordered group of characters or shapes from which an attached data processor (for example a microcomputer) can derive useful information about the object (e.g. its serial number, type, model, price, etc.). Symbols/barcodes are available in a variety of shapes and sizes. Two of the most commonly employed symbol types used in marking and identifying objects are the so-called one-dimensional barcode, consisting of a sequence of bars and spaces of varying width, and the so-called two-dimensional barcode consisting of a two-dimensional array of dots or rectangles.
In typical symbology reading, the symbols/barcodes are identified by first locating a fixed pattern, e.g., a finder pattern. If the fixed pattern is damaged or absent, the reader cannot read the symbol. In recent attempts to deal with damaged fixed patterns, efforts have included determining a location of the corners of a rectangular symbol. However, these attempts require identifying fixed points in the symbols/barcodes and are useless if those fixed points cannot be located due to the symbol being damaged.
A need exists for improved systems and methods for decoding symbols, and in particular, to overcome the shortcomings relating to a symbol/barcode that has a damaged or absent fixed pattern.